A variety of devices providing delayed turn off and intended as replacements for wall mounted switches have long been known in the art. These devices have proven quite useful in automatically controlling electrical devices such as garage or bedroom lights.
U.S. Pat. No. 4,389,599 issued to Jabor is typical of many such devices and discloses a delay circuit for delaying the turn off of a light bulb after the switch has been turned off. The Jabor device includes two leads to be connected in parallel with an existing single pole switch, however there is no option provided for manual operation which would allow use of the switch without initiation of the delayed turn off. The delayed turn off operates whenever the switch is turned off.
U.S. Pat. No. 4,494,012 issued to Coker is typical of other prior art devices and shows a timer device including a manual switch having "on", "off" and "timer" positions. This timer is configured as a direct replacement for existing wall-mounted switch units. It therefore has the desirable option of manual or automatic operation but uses an integral three position switch means to provide this option. Therefore the consumer is obligated to replace the existing wall mounted switch with the three position switch and compatible face plate which may not satisfy aesthetic requirements or match existing decor and also represents an added expense for the consumer. Also there is no provision for adjustment of the time delay period to meet the specific requirements of the operator.
Accordingly, a primary objective of the present invention is to provide a new and improved circuit for the optional delayed turn off of electrical loads such as lights.